A fiber manufacturer's customers demand consistency in performance from the fibers provided by the manufacturer. In other words, the manufacturer's customers require that the properties of any particular fiber not vary appreciably from batch to batch of that fiber as the different batches of that fiber are produced over several years. The fiber manufacturer, however, has a need to be able to identify fiber from different production batches, while maintaining the consistency and uniformity that the customers require. Much notoriety has been given to fiber identification in criminology, for example, as a way to bring murderers or other criminals to justice. Manufacturers also, however, have other more mundane and practical reasons for needing to identify the production batch of particular fibers. So it has long been desirable to find a cheap yet effective system for identifying fibers. Previously, for instance, one method has been to add a chemical or nuclear marker to the fiber, but this method has added expense and complications and has had disadvantages, such as the ease with which some one other than the fiber manufacturer can add the same marker, after manufacture, and so confuse this system for identification.
In particular, there has long existed a need for an economical way to identify and differentiate resilient multi-void fibers (especially polyester multi-void fibers) that are crimped and used as fiberfill in products such as batts, fiberballs and other filling materials and filled articles, such as pillows, filled apparel, comforters, cushions and such like bedding and furnishing material. As indicated, it is important that any identifier system should not change the performance and properties of the fibers.
Examples of such crimped multi-void resilient filling fibers include those disclosed by Champaneria et al in U.S. Pat. No. 3,745,061, and in EP A2 0 067 684 (Jones et al), having 4 voids (sometimes referred to as holes) with a solid axial core, and by Broaddus in U.S. Pat. No. 5,104,725, having 7 or more voids, arranged with a central void and other voids arranged around the central void. Both 4-void and 7-void polyester filling fibers have been produced and sold commercially, and have been used as fiberfill. Broaddus compared properties of fiberfill comprising his 7-void filling fibers with those of fiberfill comprising prior commercial 4-void filling fibers and also with those of fiberfill comprising hollow filling fibers. The most important properties to compare for use as fiberfill are the bulk properties; measurement of bulk properties (referred to as TBRM for "Total Bulk Range Measurement") have been described, e.g., by Tolliver in U.S. Pat. No. 3,772,137, and so have frictional properties (that were also measured by Broaddus and are also important for fiberfill). Both of these crimped multi-void filling fibers have shown significant advantages over resilient crimped hollow filling fibers (such as disclosed by Tolliver in U.S. Pat. No. 3,772,137) in their performance as filling materials, especially when such multi-void filling fibers have had a smooth round peripheral surface. The disclosure of each of the above patent specifications is expressly included herein by reference.
In addition to the 4-void and 7-void filling fibers that were already commercially available, multi-void filling fibers have recently been invented with a smooth round peripheral surface and with only three longitudinal voids, as disclosed by Hernandez et al. in allowed application Ser. No. 08/315,748 (DP-6320), filed Sep. 30, 1994, the disclosure of which is also included herein, by reference.